WinCE平臺下C＃引用API（GDI）一個值得警惕的記憶體洩漏
由於C＃精簡框架集繪圖函式不支援圓角矩形，所以引用了相關的API。
[DllImport("//windows//coredll.dll", EntryPoint = "RoundRect")] private static extern int CeRoundRect(IntPtr hdc, int X1, int Y1, int X2, int Y2, int X3, int Y3);
這是有記憶體洩漏的原始碼：
public static int RoundRect(Graphics e, Pen pen, SolidBrush brush, int X1, int Y1, int X2, int Y2, int X3, int Y3) { IntPtr hpen; IntPtr hbrush;
if(pen!=null) { hpen = CreatePen((DashStyle.Solid == pen.DashStyle) ? 0 : 1, (int)pen.Width, SetRGB(pen.Color.R, pen.Color.G, pen.Color.B)); //建立GDI畫筆 } else { hpen = GetStockObject(8); //空畫筆 }
if (brush!= null) { hbrush = CreateSolidBrush(SetRGB(brush.Color.R, brush.Color.G, brush.Color.B)); //brush.Color.ToArgb()); } else { hbrush = GetStockObject(5); }
//pen.Dispose(); //brush.Dispose();
IntPtr hdc = e.GetHdc(); //--------------------- SelectObject(hdc, hbrush); SelectObject(hdc, hpen); int intRet=RoundRect(hdc, X1, Y1, X2,Y2, X3, Y3);
DeleteObject(hbrush); DeleteObject(hpen); //--------------------- e.ReleaseHdc(hdc); return intRet; }
這是沒有問題的原始碼：
public static int RoundRect(Graphics e, Pen pen, SolidBrush brush, int X1, int Y1, int X2, int Y2, int X3, int Y3) { IntPtr hpen,old_pen; IntPtr hbrush, old_brush;
if(pen!=null) { hpen = CreatePen((DashStyle.Solid == pen.DashStyle) ? 0 : 1, (int)pen.Width, SetRGB(pen.Color.R, pen.Color.G, pen.Color.B)); //建立GDI畫筆 } else { hpen = GetStockObject(8); //空畫筆 }
if (brush!= null) { hbrush = CreateSolidBrush(SetRGB(brush.Color.R, brush.Color.G, brush.Color.B)); //brush.Color.ToArgb()); } else { hbrush = GetStockObject(5); }
//pen.Dispose(); //brush.Dispose();
IntPtr hdc = e.GetHdc(); //--------------------- old_brush=SelectObject(hdc, hbrush); old_pen=SelectObject(hdc, hpen); int intRet=RoundRect(hdc, X1, Y1, X2,Y2, X3, Y3);
SelectObject(hdc, old_brush); SelectObject(hdc, old_pen); DeleteObject(hbrush); DeleteObject(hpen); //--------------------- e.ReleaseHdc(hdc); return intRet; }
看出程式碼的區別來了沒有？洩漏的原因其實很簡單，就是沒有重新選入舊的畫筆畫刷。同樣的程式（當然PC端的API庫是GDI32）在上位機Window XP平臺上沒有什麼問題（測試大約3天以上），而在WinCE平臺確非常明顯，大約1～3個小時（視圓角矩形繪圖的多寡而定），該程式就會記憶體耗盡而死。